Laser distance finders have advantages of being convenient for use, high accuracy, and short measuring time. Laser distance finders are widely used in a variety of applications, such as architecture, exploration, construction and so on.
A known laser distance finder usually comprises a laser generating device, a collimating lens positioned at an emitting end of the laser generating device for converting a laser beam generated from the laser generating device into a collimating measuring beam, a receiving lens disposed on one side of the laser generating device for receiving a reflected measuring beam from an object to be measured and focusing it into an image, an optoelectronic detector disposed in the distance finder for receiving the image of the reflected measuring beam and converting optical signals therein into corresponding electrical signals which is processed to obtain a distance measuring result.
The distance measuring result derived from the electrical signals converted from the optical signals received by the optoelectronic detector contains a distance by which the measuring beam is transmitted in the distance finder. And during the distance measuring, an accuracy of the measuring result is directly affected by drift errors of electrical signals transferred in circuit which are caused by self-heating of electronics elements of the circuit and environmental temperature influences. Therefore, an internal reference distance having a known length is provided in the distance finder to improve the measuring accuracy, and a reflective member is arranged in an optical path of the collimating measuring beam. When measuring an external distance, the reflective member is on a non-blocking position so that the collimating measuring beam is allowed to be projected out of the distance finder. When measuring the internal reference distance, the reflective member is on a blocking position to reflect the collimating measuring beam in the distance finder to form an internal optical path.
A button directly connected to the reflective member is provided in the conventional laser distance finder for a user to manually change the positions of the reflective member, which is inconvenient. In some other optical distance finders, a motor is provided to drive the reflective member to swivel, continuously supplying power to provide current to the motor so that the reflective member can be kept in a desired position when the reflective member is swiveled onto the desired position. This device consumes a great deal of power and is particularly disadvantageous to the distance finder mainly powered by battery cells. In addition, the laser distance finder is so sensitive that the current continuously provided to the motor will influence the measuring result, reducing the measuring accuracy.